1. Field of the Invention
The present invention relates generally to medical apparatus and methods. More particularly, the present invention relates to methods and apparatus for decompressing ureteral stones and blockages in other body lumens.
Calculi or “stones” can form in the kidneys as low solubility waste materials precipitate out of solution. The resulting “kidney stones” can pass into the ureter and, so long as the stones are relatively small, can pass from the patient through normal urination. Larger kidney stones which lodge in the ureter are referred to as ureteral stones can cause pain, particularly when they occlude the ureter and cause pressure to build in the kidneys.
Ureteral stones can be treated in a variety of ways. Most commonly, patients are given pain medication and fluids and the stones are allowed naturally pass from the ureter. In the remaining cases, where the pain is more severe or the build-up of pressure threatens to harm the kidney, the patient may be treated more aggressively to remove or destroy the stone. Common treatments include surgery, shock wave lithotripsy, laser lithotripsy, and the like.
Of particular interest to the present invention, stents may be placed from the kidney to the bladder to bypass the ureteral stone and allow drainage. Placement of such stents is often after prior treatment. Although it may be desirable to place a stent before treatment to decompress the kidney and relieve both pressure and pain, such prophylactic stent placement is rare. Stent placements are typically performed in an operating room where anesthesia and fluoroscopic imaging are available to aid and verify stent positioning. The need to use an operating room is a disadvantage of present procedure The risk of traumatizing and/or perforating the ureteral wall as a significant length of stent, is advanced past the stone in order to anchor one end in the kidney is another disadvantage of the present procedures. Furthermore, should the stone be dislodged and forced up the ureter, the procedure will be prolonged and the risk of trauma to the patient is increased.
For these reasons, it would be desirable to provide improved ureteral stent designs and methods for their placement. In particular, it would be desirable if the stents had a very low profile for placement, did not require anchoring within the kidney, and could be introduced without the need for full anesthesia and in settings other than an operating room. At least some of these advantages will be met by the inventions described hereinbelow.
2. Description of the Background Art
U.S. Pat. No. 6,709,465 and Published Application No. 2005/00600023 describe ureteral stents comprising a series of adjacent expanding structures for anchoring in the ureter. The use of an everting sleeve composed of thin, tensilized polytetrafluoroethylene for introducing catheters to body lumens is described in U.S. Pat. Nos. 5,531,717; 5,676,688; 5,711,841; 5,897,535; 6,007,488; 6,240,968; and EP605427B1. A wire basket for advancing stone fragment through a body lumen during lithotripsy procedure is available under the Stone Cone tradename from Boston Scientific Corporation. See Published U.S. Application No. 2003/0120281. Copending application Ser. No. 10/794,337, filed on Mar. 5, 2004, the full disclosure of which is incorporated herein by reference, describes a sheath delivery system that could be used in performing some of the methods described herein.